Nanocellulose

Abstract

A nanocellulose material of plant origin comprising nanocellulose particles or fibres derived from a plant material having a hemicellulose content of 30% or higher (w/w) (calculated as a weight percentage of the lignocellulosic components of the material). The nanocellulose may have an aspect ratio of greater than 250. The nanocellulose may be derived from plant materials having C4 leaf morphology. The plant material may be obtained from arid Spinifex. The nanocellulose can be made using mild processing conditions.

Claims

1. A nanocellulose material that is of plant origin and comprises nanocellulose particles or fibres derived from a plant material, wherein the nanocellulose material has a hemicellulose content of 30% w/w or greater, wherein the nanocellulose material comprises nanocellulose particles or fibres having a diameter of up to 20 nm.

2. The nanocellulose material as claimed in claim 1 wherein the plant material has a hemicellulose content of from 30 to 50% w/w and the nanocellulose material has a hemicellulose content of from 30 to 50% w/w.

3. The nanocellulose material as claimed in claim 2 wherein the plant material has a hemicellulose content of from 30 to 45% w/w and the nanocellulose material has a hemicellulose content of from 30 to 45%.

4. The nanocellulose material as claimed in claim 3 wherein the plant material has a hemicellulose content of from 32 to 38% w/w and the nanocellulose material has a hemicellulose content of from 32 to 38%.

5. The nanocellulose material as claimed in claim 4 wherein the plant material has a hemicellulose content of from 32 to 36% w/w and the nanocellulose material has a hemicellulose content of from 32 to 36%.

6. The nanocellulose material as claimed in claim 1 wherein the nanocellulose material has an aspect ratio of at least 250.

7. The nanocellulose material as claimed in claim 6 wherein the nanocellulose material has an aspect ratio of between 250 to 10,000.

8. The nanocellulose material as claimed in claim 7 wherein the nanocellulose material has an aspect ratio of between 250 to 5000.

9. The nanocellulose material as claimed in claim 8 wherein the nanocellulose material has an aspect ratio of between 250 to 1000.

10. The nanocellulose material as claimed in claim 9 wherein the nanocellulose material has an aspect ratio of between 266 to 958.

11. The nanocellulose material as claimed in claim 1 wherein the nanocellulose is derived from a plant material having C4 leaf anatomy.

12. The nanocellulose material as claimed in claim 1 wherein the nanocellulose material comprises cellulose nanocrystals (CNC) or nanofibrillated cellulose (NFC).

13. The nanocellulose material as claimed in claim 1 wherein the nanocellulose material comprises nanocellulose particles or fibres having a diameter of up to 15 nm.

14. The nanocellulose material as claimed in claim 13 wherein the nanocellulose material comprises nanocellulose particles or fibres having a diameter of up to 10 nm.

15. The nanocellulose material as claimed in claim 14 wherein the nanocellulose material comprises nanocellulose particles or fibres having a diameter of up to 8 nm.

16. The nanocellulose material as claimed in claim 1 wherein the nanocellulose material comprises nanocellulose particles or fibres having a length that falls within the range of from 200 nm up to 10 m.

17. The nanocellulose material as claimed in claim 1 wherein the nanocellulose material is derived from plant material in which an amount of hemicellulose in the plant material is greater than an amount of lignin in the plant material.

18. The nanocellulose material as claimed in claim 1 wherein the nanocellulose material is derived from plant material and the plant material is derived from a drought-tolerant grass species.

19. The nanocellulose material as claimed in claim 18 wherein the plant material is derived from arid grass species.

20. The nanocellulose material as claimed in claim 1 wherein the nanocellulose material is derived from plant material and the plant material is derived from Australian native arid grass known as spinifex from the genera Triodia, Monodia, or Symplectrodia, T. pungens, T. shinzii, T. basedowii, or T. longicep.

21. The nanocellulose material as claimed in claim 1 wherein the nanocellulose material is derived from plant material and the plant material is derived from Digitaria sanguinalis (L.) Scopoli, Panicum coloratura L. var. makarikariense Goossens, Brachiaria brizantha (Hochst. Ex A. Rich) Stapf, D. violascens Link, P. dichotomiflorum Michaux, B. decumbens Stapf, Echinochloa crus-galli P. Beauv., P. miliaceum L., B. humidicola (Rendle) Schweick., Paspalum distichum L., B. mutica (Forsk.) Stapf, Setaria glauca (L.) P. Beauv, Cynodon dactylon (L.) Persoon, Panicum maximum Jacq., S. viridis (L.) P. Beauv, Eleusine coracana (L.) Gaertner, Urochloa texana (Buckley) Webster, Sorghum sudanense Stapf, E. indica (L.) Gaertner, Spodiopogon cotulifer (Thunb.) Hackel, Eragrostis cilianensis(Allioni) Vignolo-Lutati, Chloris gayana Kunth, Eragrostis curvula, Leptochloa dubia, Muhlenbergia wrightii, E. ferruginea (Thunb.) P. Beauv., Sporobolus indicus R. Br. var. purpureo-suffusus (Ohwi) T. Koyama, Andropogon gerardii, Leptochloa chinensis (L.) Nees, grasses of the Miscanthus genus (elephant grass), plants of the genus Salsola including Russian Thistle, ricestraw, wheat straw, and corn stover, and Zoysia tenuifolia Willd, or derived from plant material derived from arid grasses, Anigozanthos, Austrodanthonia, Austrostipa, Baloskion pallens, Baumea juncea, Bolboschoenus, Capillipedium, Carex bichenoviana, Carec gaudichaudiana, Carex appressa, C. tereticaulis, Caustis, Centrolepis, Chloris truncate, Chorizandra, Conostylis, Cymbopogon, Cyperus, Desmocladus flexuosa, Dichanthium sericeum, Dichelachne, Eragrostis, Eurychorda complanata, Evandra aristata, Ficinia nodosa, Gahnia, Gymnoschoenus sphaerocephalus, Hemarthria uncinata, Hypolaeana, Imperata cylindrical, Johnsonia, Joycea pallid, Juncus, Kingia australis, Lepidosperma, Lepironia articulate, Leptocarpus, Lomandra, Meeboldina, Mesomelaena, Neurachne alopecuroidea, Notodanthonia, Patersonia, Poa, Themedo triandra, Tremulina tremula, Triglochin, Triodia and Zanthorrhoea, Aristida pallens (Wire grass), Andropogon gerardii (Big bluestem), Bouteloua eriopoda (Black grama), Chloris roxburghiana (Horsetail grass), Themeda triandra (Red grass), Panicum virgatum (Switch grass), Pennisetum ciliaris (Buffel grass), Schizachyrium scoparium (Little bluestem), Sorghatrum nutans (Indian grass), Ammophila arenaria (European beach grass) and Stipa tenacissima (Needle grass).

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a flowchart showing the most commonly used general protocol for producing CNC in the prior art;

(2) FIGS. 2A and 2B show a comparison between common established procedures for producing MFC (FIG. 2A) and common established procedures for producing NFC (FIG. 2B);

(3) FIG. 3 shows SEM micrographs showing cross-sections of a native Triodia fibre; a) low magnification overview, b) parenchyma cells showing a high surface area, flaky morphology, and c) nodular structures;

(4) FIG. 4 shows an example process for plant feedstock preparation and pulping in the case that both delignification and bleaching are carried out, using plant material from Triodia Pungens;

(5) FIGS. 5A and 5B show TEM images of cellulose nanocrystals/fibrils obtained from bleached spinifex pulp via acid hydrolysis (40% sulphuric acid, at 45 C. for 3 h) (scale bar: 200 nm). The average diameter of acid treated fibres in FIG. 5A is 41.4 nm. The nanocellulose of FIG. 5B had an average diameter of 3.40.78 nm.

(6) FIG. 6A shows a TEM image of the nanofibers obtained from spinifex after 1 pass through a HPH with the pressure of 1500 bar and FIG. 6B shows a TEM image of the nanofibers obtained from spinifex after 5 passes through HPH with the pressure of 1500 bar (scale bar is 200 nm in both cases);

(7) FIG. 7 shows a TEM image of the suspension obtained after milling a spinifex bleached pulp at 1500 rpm for 30 min in circulating setup in a ball mill. The nanofibers have a diameter of 4224 nm and a length of a few microns (scale bar: 2 m);

(8) FIG. 8 shows a TEM image of the suspension obtained after milling a spinifex bleached pulp at 3000 rpm for 20 min in batch setup showing nanofibers with a diameter of 82 nm and length of 341100 nm (scale bar: 200 nm);

(9) FIG. 9 is a graph showing dispersity of dimensions (diameter) of spinifex derived nanofibrils obtained with only a single pass through a high pressure homogenizer, based on a total of 250 measurements;

(10) FIGS. 10A and 10B are process flowcharts showing a comparison of a commonly established procedure for producing NFC (FIG. 10A) and a process for producing NFC from spinifex grass using a method in accordance with an embodiment of the present invention (FIG. 10B);

(11) FIG. 11 shows a graph of dispersity of dimensions (diameter) of fibrils obtained from a spinifex bleached pulp via high energy milling (see Example 5);

(12) FIG. 12 shows an SEM image of spinifex grass delignified via alkali treatment at 80 C.;

(13) FIG. 13 shows SEM images of the delignified spinifex grass obtained via organosolv treatment at 185 C.;

(14) FIG. 14 shows a tensile curve of spinifex NFC paper produced by homogenization and dried with a hot-press at 103 C. for 2 h with no significant force applied during drying;

(15) FIG. 15 shows ATR FTIR spectra of T. pungens fibres in their virgin state (water washed), after alkaline delignification and after bleaching;

(16) FIG. 16 shows cellulose nanofibrils produced by processing bleached pulp of Triodia Pungens in a Silverson rotor-stator unit. The scale bar is 200 nm.

(17) FIG. 17 shows cellulose nanofibrils produced by processing bleached pulp of Triodia Pungens in a Silverson rotor-stator unit followed by further mechanical processing in a high pressure homogeniser. The scale bar is 1000 nm.

(18) FIG. 18 shows cellulose nanofibrils from Triodia Pungens grass processed by alkaline delignification, followed by high pressure homogenisation at 500 bar pressure (no bleaching). The scale bar is 500 nm.

(19) FIG. 19 shows cellulose nanofibrils from Triodia Pungens grass processed by alkaline delignification, followed by high pressure homogenisation at 700 bar pressure (no bleaching). The scale bar is 500 nm.

EXAMPLES

(20) Pulping

(21) The following examples used plant material derived from Australian arid spinifex (Triodia pungens). For pulping the plant material, the material was chopped to a particle size of less than 10 mm to enable easier processing and the natural fibre or cellulose fibre part was separated by delignification. In some cases delignification was followed by a bleaching treatment. The general process for pulping the plant material is shown in FIG. 5. For delignification, the fibres were first treated with either alkaline solution of low concentration or organosolv at higher temperature.

(22) Delignification of Spinifex Grass

(23) Delignification was done using two different methods;

(24) Organosolv: In this treatment a 40 w/v % ethanol solution is combined with the grass in a 2.5:1 solvent grass (v/w) ratio at 185 C. was applied for 2 hours under the pressure in an autoclave then washing was performed using a 1 M NaOH solution and finally water. This procedure was repeated once more in order to pull out the residual lignin from between the fibrils.

(25) Alkaline treatments: In alkali treatment spinifex grass was subjected to alkaline solution of 2 wt % NaOH with the solvent to grass ratio of 10:1 at 80 C. for 2 hours, then filtered and washed with water.

(26) Bleaching Spinifex Grass

(27) For bleaching delignified fibres, a 1 wt % aqueous solution of sodium chlorite at 70 C. and pH=4 (pH adjusted using glacial acetic acid) was used for an hour with 30:1 solvent to grass mass ratio under stirring until white point which the coloured substances were removed from the grass.

(28) Table 3 below shows the composition of lignocellulosic components in Triodia pungens grass following washing in water and different stages in the pulping process. It was observed that prior to chemical processing (pulping) the Spinifex grass had a hemicellulose content of 44% (w/w) and this reduced to 43% and 42% following delignification and bleaching steps respectively. In all cases, these percentage amounts are percentages of the total lignocellulosic mass of the material. Interestingly, the hemicellulose content does not decrease significantly on delignification or bleaching of the water-washed grass, allowing the high hemicellulose content of the grass to be carried through to the final nanocellulose product. This may be a result of the very mild delignification and bleaching conditions used in the method of the present invention.

(29) TABLE-US-00003 TABLE 3 Composition of lignocellulosic components in water-washed and pulp of T. pungens grass. Cellulose Hemicellulose Lignin Treatments % (w/w) % (w/w) % (w/w) Water-washed 33 44 23 Alkali delignified 31 43 26 Alkali delignified and 55 42 3 bleached Organosolv delignified 40 34 26 Organosolv delignified 60 34 8 and bleached

(30) The ATR FTIR spectra for water-washed, delignified and bleached T. pungens fibres shown in FIG. 15 feature a main broad peak within the wave number range of 3000-3650 cm-1, which confirms stretching vibrations of hydroxyl (OH) groups as the principal functional group in these lignocellulosic materials.

Example 1Higher Aspect Ratio Nanofibers From Spinifex Via Acid Hydrolysis

(31) Sulphuric acid hydrolysis is a suitable chemical method for isolating cellulose nanocrystals, due to high yield and the surface charges (sulphate) created after the hydrolysis, which can facilitate the dispersion in water and other polar solvents. In a typical prior art procedure, the acid concentration varies from 35 to 65% and the temperature varies from 40 to 100 C., depending on the source. In general, if a low range of acid concentration is used, a higher temperature is used, and if a low temperature is used, a higher acid concentration is used. With spinifex grass, use of an acid concentration above 45% and a temperature above 50 C. resulted in detrimental effect on the hydrolysis, either charring or complete hydrolysis into low molecular sugars.

(32) Different methods have been applied in the prior art to prepare cellulose nanocrystals. Each of these lead to different types of nanomaterial (e.g., shape, length, and diameter), depending on the source of the cellulose and the degradation process (e.g., controlled time, temperature and acid concentration), and also the applied pre-treatment. The main process in the preparation of cellulose nanocrystal (CNCs) is based on strong acid hydrolysis under strictly controlled conditions of temperature, agitation, and time to remove amorphous, disordered or para-crystalline regions and isolate crystalline domains with higher resistance to acid attack. Removing the amorphous region has shown improvement in the crystallinity and thermal stability of extracted rod-like nanocrystals.

(33) Different concentrations of sulphuric acid solution at different temperatures were used for different times to characterize the effect of hydrolysis parameters on cellulose fibres properties.

(34) The experimental results showed that we could successfully produce cellulose nanocrystals from spinifex grass using the minimum acid concentration and lowest temperature together (we used 35% sulphuric acid at 45 C.the difference with our work is that we used the minimum for both conditions). Applying harsh treatment, such as more than 40% sulphuric acid (mostly 64% is using to hydrolysis different source of cellulose for producing cellulose nanocrystals) and higher temperature (above 50 C.), to spinifex-derived plant material damages the fibres and hydrolyses the cellulose into low molecular sugars glucose. It is worth noting that the nanocrystals obtained from spinifex grass have a very long length while the nanocrystals from the other sources of cellulose are short and straight. The highest known aspect ratio cellulose nanocrystals are obtained from marine animals called tunicates. Because of their rarity, the production of high aspect ratio CNCs is limited at a commercial scale. Production of high aspect ratio CNC s derived from plant sources was unknown prior to the present invention.

(35) FIGS. 5A and 5B show TEM image of cellulose nanocrystals/fibrils obtained from bleached spinifex pulp via acid hydrolysis (40% sulphuric acid, at 45 C. for 3 h) (scale bar: 2 m) as used in Example 1. The average diameter of acid treated fibres in FIG. 5A is 41.4 nm. A measurement of shorter fibres of an acid treated fibres which we could find the start and end point in FIG. 5B shows the average diameter of 3.40.78 nm.

Example 2Small Diameter Nanofibers From Spinifex Via Homogenisation

(36) To obtain nanofibrillated cellulose (NFC), aqueous suspensions of delignified (alkaline route) and bleached spinifex pulps (42% hemicellulose content) were homogenized using a high pressure homogeniser (EmulsiFlex-C5 homogenizer) at different solids loadings (0.1, 0.3 and 0.7% w/v) and at different pressures (1500, 1000, 350 bar). FIG. 6 shows the TEM images of the obtained nanofibers with the average width of about 3.5 nm after 1 pass (FIG. 6A) and 5 passes (FIG. 6B), through the homogeniser. Hemicellulose content was 42%.

(37) Obtaining a homogeneous suspension of nanofibers within a few number of passes with 100% yield has been beneficial. Unlike fibres from other source, there was no clogging issue encountered even after increasing the number of passes up to 15, suggesting the nanofibres could be obtained with lower energy consumption. Efficiency of this process may be further increased by increasing the solid content in suspension.

Example 3Agglomerated Nanofibres From Spinifex Via High-Energy Ball Milling

(38) As a scalable method to produce cellulose nanofibres (fibrils/crystals), we investigated high-energy ball milling (Netsch-Labstar 10, diameter of the milling chamber: 97 mm, volume of balls: 400 ml (including the interstitial space between the balls), media for grinding: water, loading of suspension: 400 ml, volume of grinding chamber: 620 ml). There have been few reports made using lab-scale (1 to 5 g scale) ball milling. Our method/set-up relies on large-scale processing. FIG. 7 shows the nanofibres (width 4224 nm) obtained from milling a delignified (alkaline) and bleached pulp (42% hemicellulose content) at 1500 rpm (lower energy) after 30 min of circulation.

(39) In another example, a pulped suspension was milled at 3000 rpm for 20 min of batch setup (high energy). FIG. 8 TEM of the resulting suspension showing the nanofibres (width was 82 nm, length was 341=100 nm) (scale bar: 200 nm). This also suggests that by applying higher energy we could further break down the nanofibres into shorter nanocrystals.

Example 4NFC Preparation Using High-Pressure Homogenizer

(40) A slurry of Spinifex pulp (alkaline delignified and bleached fibres) (42% hemicellulose) was passed through a high-pressure homogenizer (EmulsiFlex-C5.Homogenizer) This homogeniser rapidly reduces particles size from micron to nanometer scale based on the principle of dynamic high-pressure homogenisation. During the preparation of NFCs, it was found that high-pressure homogenization has a noticeable effect on the diameter of fibres. The NFCs showed a complex, web like structure. Different shape of twisted/untwisted, and curled/straight nanofibrils have the diameter less than 7 nm and several microns length even after only 1 pass through homogenizer.

(41) Applying different pressure, different slurry concentration and also different numbers of passes exhibited almost the same results on fibrils diameter and length (Table 4). All nanocellulose products had 42% hemicellulose content. In case of higher pressure, more fibrillation was observed. The most important issue when thinking about an up-scaling of the nanofibrillated cellulose production in industry is the energy consumption. So recently, several researchers have focussed on the development of less energy consuming disintegration methods using enzymatic, chemical or mechanical pre-treatment. In our process with spinifex grass, homogenisation of bleached pulp produces NFC even at first pass through the homogenizer without any clogging issues. Since the fibres were already well-fibrillated into nanoscale material at first pass, further homogenisation did not show any clogging and it only helped to fibrillate into a few nanometers. In other words, it was easier to fibrillate into nanoscale fibres at first pass (FIG. 9) whereas in the reported papers, a minimum of 6 passes or treating with acid/alkaline/polyelectrolyte was usually performed to reduce the higher number of passes which is crucial in terms of energy consumption of the process 2-4.

(42) TABLE-US-00004 TABLE 4 Average diameter of nanofibres obtained by homogenization 0.1 wt %, 0.3 wt %, 0.3 wt %, 0.3 wt %, 0.3 wt %, 1 pass 1 pass 5 pass 10 pass 15 pass 0.7 wt %, 1 pass 1500 bar 3.2 0.7 3.5 0.8 3.2 0.7 3.3 0.8 3.2 0.8 3.7 0.7 1000 bar 3.5 0.6 350 bar 3.7 1 3.7 1

(43) Process flowcharts in FIGS. 10A and 10B showing a comparison of the common established procedures for producing NFC and a process for producing NFC from spinifex grass using a method in accordance with an embodiment of the present invention. As can be seen, in the process of the present invention (FIG. 10B), the steps of chemical pre-treatment, mechanical pre-treatment and/or enzymatic pre-treatment can be omitted.

(44) With bleached ethanol and alkali treated spinifex feedstock, the present inventors were able to produce NFCs using considerably fewer (1) passes compared with 20 passes for cotton-derived feedstock prepared using much harsher multistep pretreatment steps. i.e. an order of magnitude larger energy and time required to obtain a much lower aspect ratio product. Furthermore, with spinifex the HPH could practically be run at higher suspension concentration without clogging, meaning much higher potential yields.

Example 5MFC Preparation Using High-Energy Milling, and Resultant Dimensions

(45) The milling of spinifex grass was performed in which a slurry of bleached spinifex pulp in only water was subjected to the high-energy milling (Netzsch Laboratory agitator based mill LABSTAR). FIG. 11 shows a graph of dispersity of dimensions (diameter) of fibrils obtained via high-energy milling.

(46) This example demonstrates extraction of cellulose from spinifex grass using a high-energy milling while the crystallinity of obtained nanofibrils and structure of cellulose didn't change. The nanofibrils have the diameter in the range of below 40 nm and several microns length (FIG. 11).

(47) Without wishing to be bound by theory, the present inventors believe that the milder conditions or lower energy (for chemical or mechanical methods) required for defibfillating/micronising the spinifex grass fibers into nay is likely to be attributable to the structural morphology of the fibers. FIGS. 12 and 13 show SEM images of spinifex fiber after delignification via alkali and organosolv treatment respectively. The morphology of the fibers suggests the elementary fibrils are intertwined and stacked to form microfibres which are connected together with hollow tube-like channel.

(48) It is assumed that fibres with this morphology may have evolved to adapt to the harsh drought conditions and to reduce the water evaporation.

(49) For a spinifex NFC sample prepared via 1 pass through the high-pressure homogenizer at 1500 bar, the following dimensions were measured. The average aspect ratio of nanofibrils with an average width/diameter of 320.7 nm and an average length of 1686591 nm is 527185 (with lengths ranging between 266 and 958, as measured from TEM images taken at a higher magnificationnoting some higher aspect ratio nanofibrils could not be measured due to the limited field of view). The average aspect ratio of larger diameter nanofibrils (or rather, larger bundles comprising several nanofibrils) with an average width/diameter of 10.693.9 nm and an average length of 57701700 nm is 540166 (ranging from 305 to 727, as measured from TEM images taken at low magnification to cover the whole lengthalso noting that at low magnification, the measured average diameter may be overestimated, due to limited resolution, but still the NFC bundles which were visible showed an average 10.7 nm width).

Example 6Preparation of Cellulose Nanopaper

(50) Spinifex cellulose nanopaper was produced from an aqueous NFC suspension after vacuum filtration on a Bchner funnel fitted with a cellulose acetate membrane filter (pore size: 0.45 m, diameter: 47 mm). The filtration was continued until the wet sheet of NFC was formed. The wet sheet was then dried using hot press trying at a temperature of 103 C. for 2 hours.

(51) Mechanical testing of the spinifex nanopaper was performed at room temperature using an Instron model 5543 universal testing machine fitted with a 500 N load cell. A total of five replicates of each sample with dimensions of 25 mm in length and 6 mm in width were tested at 1 mm/min strain rate with a 10 mm gauge length. The Young's modulus was determined from the slope of the initial linear region of the stress-strain curves. Maximum tensile strength is the largest stress that a film is able to sustain against applied tensile stress before the film tears. Elongation at break is the maximum percentage change in the original film length before breaking, and work to fracture is measured as the area under the stress-strain curve.

(52) The density of nanopaper was calculated by measuring dried paper's weight and dividing it by its volume calculated from the thickness by digital micrometer and its area. The corresponding porosity was estimated as the following Eq (1);

(53) $\begin{array}{cc}\mathrm{Porosity}=1-\frac{\mathrm{NFCpaper}}{\mathrm{cellulose}}& \left(1\right)\end{array}$

(54) Here .sub.NFC paper and .sub.cellulose represent density of the obtained NFC films and neat cellulose (1460 kg/m3), respectively.

(55) Mechanical properties of the nanopaper made from spinifex nanofibrils (42% hemicellulose content) are set out in the Table 5;

(56) TABLE-US-00005 TABLE 5 Mechanical properties of spinifex nanopaper produced by homogenization and dried with a hot-press at 103 C. for 2 h with no significant force Elastic Tensile Tensile Tensile Porosity Modulus Strain Strength Toughness (%) (GPa) (%) (MPa) (MJ/m.sup.3) 22 3.2 18 84 12.3

(57) FIG. 14 shows tensile curves of spinifex NFC paper produced by vacuum filtration of homogenized nanofibrils and dried with a hot-press at 103 C. for 2 h. For a given nanopaper density, the present inventors believe that the overall toughness of this spinifex derived material (i.e. area under the tensile curve) is very impressive due to the entanglements of the long fibrils enabling quite a high plastic deformation before breakage.

Example 7Silverson Processing of Bleached Pulp

(58) An aqueous suspension of delignified (alkaline) and bleached spinifex pulp (42% hemicellulose) was subjected to processing through a Silverson rotor stator homogenising unit for 5 minutes at room temperature. As shown in FIG. 16, long cellulose nanofibrils with a diameter of 5.573 nm and 42% hemicellulose content were produced.

Example 8HPH Processing of Silverson Processed Pulp

(59) An aqueous suspension of delignified (alkaline) and bleached spinifex pulp (42% hemicellulose) was subjected to processing through a Silverson rotor stator homogenising unit for 5 minutes at room temperature followed by a single pass through a high pressure homogeniser at 500 bar pressure. As shown in FIG. 17, long cellulose nanofibrils with a diameter of 8.73 nm and 42% hemicellulose content were produced. Scale bar is 1000 nm.

Example 9Cellulose Nanofibrils Produced Without Bleaching

(60) A sample of Triodia pungens grass was subjected to alkaline delignification. The delignified pulp (43% hemicellulose) was then passed through a high-pressure homogeniser at 500 bar pressure for a single pass only. The pulp was not bleached. As shown in FIG. 18, long cellulose nanofibrils with diameter of 6.80.23 nm and 43% hemicellulose content were obtained.

Example 10Cellulose Nanofibrils Produced Without Bleaching

(61) A sample of Triodia pungens grass was subjected to alkaline delignification. The delignified pulp (43% hemicellulose) was then passed through a high-pressure homogeniser at 700 bar pressure for a single pass only. The pulp was not bleached. As shown in FIG. 19, long cellulose nanofibrils with diameter of 3.91.3 nm and 43% hemicellulose content were obtained.

(62) Aspect Ratio Method of Measurement

(63) In the examples given in this specification, the following method was used to measure or determine aspect ratio:

(64) Samples of spinifex cellulose nanofibrils in water were sonicated and 1 l was spotted onto formvar coated Cu/Pd 200 mesh grids and allowed to dry. Samples were then stained with 2% uranyl acetate (aq) for 10 minutes in the absence of light then excess UA was removed and grids were allowed to dry. Grids were then examined on a JEOL 1011 TEM operating at 100 KV and captured on a SIS Morada 4K CCD camera system.

(65) For each sample, 250 measurements of diameter were randomly selected and measured from several TEM images using digital image analysis (Image J).

(66) For measuring the length of fibres, each TEM image was processed using AutoCAD software. This program allows contours to be manually drawn following the non-linear path of each cellulose nanofibre in xy space and contains tools for the subsequent calculation of contour length.

(67) Throughout this specification, the following terms have the following meanings:

(68) Microfibrillated cellulose (MFC): MFC is produced via mechanical refining of highly purified WF and PF pulps, have a high aspect ratio (20-100 nm wide, 0.5-10's m in length), are 100% cellulose, and contain both amorphous and crystalline regions.

(69) Wood Fibre (WF). (a) (Bot.) Fibrovascular tissue. (b) Wood comminuted, and reduced to a powdery or dusty mass.

(70) Plant fibre (PF)1: fibre derived from plants [syn: plant fibre, plant fibre]

(71) Nanofibrillated cellulose (NFC): NFC particles are finer cellulose fibrils produced when specific techniques to facilitate fibrillation are incorporated in the mechanical refining of WF and PF have a high aspect ratio (3-20 nm wide, 500-2000 nm in length), are 100% cellulose and contain both amorphous and crystalline regions.

(72) Cellulose nanocrystals (CNC): CNCs are rod-like or whisker shaped particles remaining after acid hydrolysis of WF, PF, MCC, MFC, or NFC. These particles have also been named nanocrystalline cellulose, cellulose whiskers, cellulose nanowhiskers and cellulose microcrystals (in the early literature). CNCs have a high aspect ratio (3-5 nm wide, 50-500 nm in length), are 100% cellulose, are highly crystalline (54-88%)

(73) Tunicate cellulose nanocrystals (t-CNC): Particles produced from the acid hydrolysis of tunicates are called t-CNCs. The ribbon-like shaped t-CNCs have a height of B8 nm, a width of B20 nm, a length of 100-4000 nm (typical aspect ratios 70-100), are 100% cellulose, are highly crystalline (85-100%).

(74) Microcrystalline cellulose (MCC): Cellulose microparticles produced commercially via regular pre-treatments (delignification, bleaching, grinding and/or acid hydrolysis and back-neutralization with alkali). Their width 10-50 m and length 10-500 m. They are the current commercial source for producing MFC, NFC and CNCs.

(75) In the present specification and claims (if any), the word comprising and its derivatives including comprises and comprise include each of the stated integers but does not exclude the inclusion of one or more further integers.

(76) Reference throughout this specification to one embodiment or an embodiment means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearance of the phrases in one embodiment or in an embodiment in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more combinations.

(77) In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described comprises preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims (if any) appropriately interpreted by those skilled in the art.